The present invention relates to the use of metallocene waxes, their oxidates and blends thereof with further waxes, and also the corresponding micronisates, for coating materials.
In the preparation of coating materials, waxes are generally added in a concentration of 0.01-10%. The waxes in question are PE waxes, PTFE waxes, PP waxes, amide waxes, FT paraffins, montan waxes, natural waxes, macrocrystalline and microcrystalline paraffins, polyethylene copolymers, sorbitan esters and metallocene waxes, and also blends thereof, as disclosed in EP-A-0 890 619. The blends may be present in different combinations, both as powder mixtures and as melt mixtures.
These waxes are added in the form of flakes, granules, powders, dispersions, emulsions or micronisates, the preferred use form being regardable as a finely micronized powder with particle sizes up to 4 xcexcm in DV50 value. (DV50 value: 50% of the wax particles are smaller than or equal to 4 xcexcm). These waxes are used in order to achieve the following effects in the coating materials:
better scratch resistance
better abrasion resistance
better dispersing of pigments
better pigment stability
improvement in sedimentation tendency
improvement in redispersion of pigments
active orienting substance for effect pigments
effective flatting
satisfactory feel
improvement in lubricity
improvement in metal marking
achieving effective incorporation of effect pigments
influencing of rheological properties
better blocking resistance
better sandability
degassing additive in powder coatings
additive for increasing throughput in powder coatings.
These wax additives can be used in all coating systems (e.g., low solids, medium solids, high solids, solvent-based coating materials, aqueous or water-dilutable coating materials, powder coating materials, physically drying coating systems, chemically curing coating materials, and radiation-curing coating materials, such as UV coating materials, for example).
Since pure polyethylene waxes and metallocene waxes cannot be used in all coating systems, especially not in aqueous systems, use is also made of wax oxidates.
Since the individual types of wax display different effects in the coating materials, it is preferred to use wax mixtures of PE waxes, PTFE waxes, PP waxes, amide waxes, FT paraffins, montan waxes, natural waxes, macrocrystalline and microcrystalline paraffins, polyethylene copolymers, sorbitan esters and metallocene waxes in order to combine the abovementioned effects with one another and to obtain corresponding improvements in coating materials.
It was an object of the invention to find wax mixtures, for use in coating materials, which exhibit a particularly large number of the effects set out above. Surprisingly, the mixtures with metallocene waxes showed the most marked improvements. With these mixtures, a particular improvement is obtained in the grindability for the production of wax micronisates; in other words, the yields are increased.
A further advantage of using waxes produced by the metallocene process is their ready grindability, for which reason fewer auxiliaries are consumed in this case than in the case of wax mixtures comprising waxes produced, for example, with the Ziegler-Natta process.
The invention provides for the use of mixtures of waxes which comprise
a) a homopolymer or copolymer of C2-C18 xcex1-olefins, prepared by means of metallocene catalysis, and also degradation waxes produced from relatively high-chain-length polyolefins produced by means of metallocene catalysis, and, as auxiliaries, one or more other waxes selected from the group consisting of
b) PE waxes,
c) PTFE waxes,
d) PP waxes,
e) amide waxes,
f) FT paraffins,
g) montan waxes,
h) natural waxes,
i) macrocrystalline and microcrystalline paraffins,
j) polar polyolefin waxes, or
k) sorbitan esters,
l) polyamides,
m) polyolefins,
n) PTFE,
o) wetting agents,
p) silicates
for improving the properties of coating materials.
The invention further provides coating materials comprising the wax mixtures described.
The homopolymer or copolymer of C2-C18 xcex1-olefins prepared by means of metallocene catalysis (a) preferably have the following properties:
Suitable polyolefin waxes include homopolymers of ethylene or propylene or copolymers of ethylene or propylene with one another or with one or more 1-olefins. 1-Olefins used include linear or branched olefins having 4-18 carbon atoms, preferably 4-6 carbon atoms. These olefins may have an aromatic substitution which is in conjugation with the olefinic double bond. Examples of such compounds are 1-butene, 1-hexene, 1-octene or 1-octadecene, and also styrene. Preference is given to copolymers of ethylene with propene or 1-butene. Ethylene copolymers of this kind have ethylene contents of 70-99.9% by weight, preferably 80-99% by weight.
Especially suitable polyolefin waxes are those having a dropping point of between 90 and 160xc2x0 C., preferably between 100 and 155xc2x0 C., a melt viscosity at 140xc2x0 C. of between 10 and 10 000 mPas, preferably between 50 and 5 000 mPas, and a density at 20xc2x0 C. of between 0.89 and 0.96 g/cm3, preferably between 0.91 and 0.94 g/cm3.
Also suitable are metallocene waxes modified by oxidation, such as may be obtained, for example, by treating the wax melt with air in accordance with EP-A-0 896 591. The disclosure content of this document in respect of the oxidative treatment of wax melts is hereby incorporated into the present specification by reference.
Metallocene catalysts for preparing the polyolefin waxes are chiral or nonchiral transition metal compounds of the formula M1Lx. The transition metal compound M1Lx contains at least one central metal atom M1 to which at least one xcfx80 ligand, e.g., a cyclopentadienyl ligand, is attached. Furthermore, substituents, such as halogen, alkyl, alkoxy or aryl groups, for example, may be attached to the central metal atom M1. M1 is preferably an element from main group III, IV, V or VI of the periodic table of the elements, such as Ti, Zr or Hf. Cyclopentadienyl ligand comprehends unsubstituted cyclopentadienyl radicals and substituted cyclopentadienyl radicals such as methylcyclopentadienyl, indenyl, 2-methylindenyl, 2-methyl-4-phenylindenyl, tetrahydroindenyl or octahydrofluorenyl radicals. The xcfx80 ligands may be bridged or non-bridged, with both single and multiple bridgesxe2x80x94including bridges via ring systemsxe2x80x94being possible. The metallocene designation also embraces compounds having more than one metallocene fragment, known as polynuclear metallocenes. These may have arbitrary substitution patterns and bridging variants. The individual metallocene fragments of such polynuclear metallocenes may be both identical to one another and different from one another. Examples of such polynuclear metallocenes are described, for example, in EP-A-0 632 063. Examples of general structural formulae of metallocenes and also of their activation with a cocatalyst are given, inter alia, in EP-A-0 571 882. The disclosure contents of these subjects in the two documents is hereby incorporated by reference.
Additive b) comprises, in preferred embodiments, polyethylene homopolymer and copolymer waxes which have not been prepared by means of metallocene catalysis and which have a number-average molecular weight of from 700 to 10 000 g/mol with a dropping point of between 80 and 140xc2x0 C.
Additive c) comprises in preferred embodiments polytetrafluoroethylene having a molecular weight of between 30 000 and 2 000 000 g/mol, in particular between 100 000 and 1 000 000 g/mol.
Additive d) comprises, in preferred embodiments, polypropylene homopolymer and copolymer waxes which have not been prepared by means of metallocene catalysis and which have a number-average molecular weight of from 700 to 10 000 g/mol with a dropping point of between 80 and 160xc2x0 C.
Additive e) comprises, in preferred embodiments, amide waxes preparable by reacting ammonia or ethylenediamine with saturated and/or unsaturated fatty acids. The fatty acids comprise, for example, stearic acid, tallow fatty acid, palmitic acid or erucic acid.
Additive f) comprises, in preferred embodiments, FT paraffins having a number-average molecular weight of from 400 to 800 g/mol with a dropping point from 80 to 125xc2x0 C.
Additive g) preferably comprises montan waxes, including acid waxes and ester waxes having a carboxylic acid carbon chain length of from C22 to C36.
The ester waxes preferably comprise reaction products of the montanic acids with monohydric or polyhydric alcohols having 2 to 6 carbon atoms, such as ethanediol, butane-1,3-diol or propane-1,2,3-triol, for example.
Additive h) in one preferred embodiment comprises carnauba wax or candelilla wax.
Additive i) comprises paraffins and microcrystalline waxes which are obtained in the course of petroleum refining. The dropping points of such paraffins are preferably between 45 and 65xc2x0 C., those of microcrystalline waxes of this kind preferably between 73 and 100xc2x0 C.
Additive j) comprises, in preferred embodiments, polar polyolefin waxes preparable by oxidizing ethylene or propylene homopolymer and copolymer waxes or grafting them with maleic anhydride. Particularly preferred starting material for this purpose comprises polyolefin waxes having a dropping point of between 90 and 165xc2x0 C., in particular between 100 and 160xc2x0 C., a melt viscosity at 140xc2x0 C. (polyethylene waxes) or at 170xc2x0 C. (polypropylene waxes) of between 10 and 10000 mPas, in particular between 50 and 5000 mPas, and a density at 20xc2x0 C. of between 0.85 and 0.96 g/cm3.
Additive k) comprises, in preferred embodiments, reaction products of sorbitol with saturated and/or unsaturated fatty acids and/or montanic acids. The fatty acids comprise, for example, stearic acid, tallow fatty acid, palmitic acid or erucic acid.
Additive l) preferably comprises ground polyamides, examples being polyamide-6, polyamide-6,6 or polyamide-12. The particle size of the polyamides is preferably in a range of 5-200 xcexcm, in particular 10-100 xcexcm.
Additive m) comprises polyolefins, i.e., for example, polypropylene, polyethylene or copolymers of propylene and ethylene of high or low density with molar weights of preferably from 10 000 to 1 000 000 D, in particular from 15 000 to 500 000 D, as numerical averages of the molecular weight, whose particle size as a result of grinding is in the range of preferably 5-200 xcexcm, in particular 10-100 xcexcm.
Additive n) comprises thermoplastic PTFE having a molar weight of preferably 500 000-10 000 000 D, in particular 500 000-2 000 000 D, as numerical average, whose particle size as a result of grinding is in the range of preferably 5-200 xcexcm, in particular 10-100 xcexcm.
Additive o) comprises amphiphilic compounds which generally lower the surface tension of liquids. The wetting agents comprise, for example, alkyl ethoxylates, fatty alcohol ethoxylates, alkylbenzenesulfonates or betaines.
Additive p) comprises silicates which are not used as filler or pigment in the formulas. It is preferred to use silicas or talc.
The proportion of ingredient a) to ingredients b) to p) may be varied in the range from 1 to 99% by weight a) to 1 to 99% by weight b) to p). Where a mixture of two or more of ingredients b) to p) is used, the indicated amount applies to the sum of the amounts of these ingredients.
In one preferred embodiment, the waxes are used in micronized form for the purpose according to the invention. Particular preference is given to the use of polyolefin wax and optionally admixed auxiliaries and additives as an ultrafine powder with a particle size distribution d90 less than 40 xcexcm.
Parameters improved include the flatting of the coating materials, the dispersibility and stability (sedimentation tendency or bodying tendency) in coating materials and dispersions, an improvement in the slip, hardness and abrasion resistance, an increase in the throughput and improvement in pigment dispersion in powder coating materials, and better antiblocking and handling sensation (soft feel). The wax mixtures generally comprise powder mixtures and/or melt mixtures.